There are many known versions of such devices, in which the transmission block has constant intrinsic characteristics. These are particularly shock mounts or elastic bolsters and elastic couplings in which the material of the transmission block or transmission blocks is, for example, an elastomeric material.
Such devices are passive devices, that is to say their force transmission behaviour varies only as a function of the value of the forces or torques which they have to transmit.
The object of the present invention is to provide a version of a force transmission device which is active, that is to say the force transmission behaviour of which can be varied.
To achieve this, the invention provides a device for the mechanical transmission of forces between a first input element and a second output element, characterised in that it comprises an input member connected to the first element, an output member connected to the second element and a transmission block which is interposed between these two members and is capable of experiencing elastic deformation under the action of the compressive forces exerted on it by the two members when these are displaced relative to one another in the main force transmission direction, and in that it comprises controlled means for varying the rigidity of the transmission block in the said main direction by exerting a control force on it.
According to other characteristics of the invention:
the control force is exerted on the transmission block in a direction different from the said main direction;
the transmission block comprises two plane opposite end faces which each interact respectively with the input member and the output member, the direction of the control force being substantially parallel to the said end faces;
the transmission block comprises at least one central layer of elastically deformable material, to the opposite faces of which are fastened two rigid end plates which delimit the said end faces of the transmission block;
the transmission block comprises a stack of layers of elastically deformable material, between which rigid plates are arranged;
each layer of elastically deformable material is a thin layer of elastomeric material, and each rigid plate is a metal plate adhesively bonded to the elastomeric material;
the two end faces of the elastically deformable transmission block are in abutment against two mutually confronting reaction surfaces of the device, the device comprising a wedge-shaped control-force exertion member which penetrates into the transmission block in order to bring about the putting under compression, by a wedging effect, of the two opposite parts of the transmission block, each of which is delimited, on the one hand, by one of the two end faces of the transmission block and, on the other hand, by the corresponding inclined face of the control-force exertion member;
the two inclined faces of the control-force exertion member form the same angle relative to the main force transmission direction;
the control-force exertion member is interposed between two rigid plates of the transmission block.
In its use for transmitting a torque, the device according to the invention is characterised in that the input member and the output member are mounted movably in rotation relative to one another, in that each of the two members comprises at least one tab which is offset radially relative to the common axis of rotation and which extends opposite the corresponding tab of the other of the two members, and in that at least one controlled-rigidity transmission block is arranged between the two mutually confronting faces of the two associated tabs.
According to other characteristics of the invention:
each of the two input and output members comprises a series of tabs distributed uniformly about the axis, the tabs of each of the two members being of equal number and alternating with one another, and transmission blocks being arranged between the mutually confronting faces of each of the pairs of tabs associated with the two members;
the control-force exertion member is a member capable of being displaced axially relative to the two members, in order to vary the control force, and it comprises a series of wedges, each of which penetrates into a transmission block; or
the control-force exertion member comprises a plurality of wedges, each of which penetrates radially into a transmission block, and means for displacing the wedges simultaneously.